What is your thinking as to why there is fluid beneath both filters?
Just changing the filters won't solve a hydraulic leak(s).
What do you believe to be the cause of the leak(s). Is it possible a hydraulic line or fitting is leaking/ ruptured?
Hydraulic filters are not cheap, before you go changing them make sure you know- if possible, where the leak is coming from...
Rather than try to reuse fluid which has drained out I'd just catch the fluid in a large oil drain pan and then refill the trans based on what drained out. And make sure to check it again after filling it to make sure its up to the mark on the stick. If you're quick about getting each filter back on you should not loose any significant amount of fluid just changing filters. It's when you drain the fluid from the drain plugs that it is near impossible to stop the flow or reinsert the drain plug - but according to what I understood that is NOT what you are trying to do.
Post back what your thinking is as to location of leak(s) before proceeding further.